Coater having substrate cleaning device and coating deposition methods employing such coater

ABSTRACT

A coater having a substrate cleaning device is disclosed. Also disclosed are methods of processing substrates in a coater equipped with a substrate cleaning device. The substrate cleaning device comprises an ion gun (i.e., an ion source) that is positioned beneath a path of substrate travel (e.g., beneath a substrate support) extending through the coater and that is adapted for treating a bottom major surface of a substrate. Certain embodiments involve an upward coating apparatus that is further along the path of substrate travel than the substrate cleaning device. In some embodiments of this nature, the upward coating apparatus is configured for depositing a photocatalytic coating upwardly onto the bottom major surface of the substrate. Certain embodiments of the invention involve a downward coating apparatus, wherein the substrate cleaning device is further along the path of substrate travel than the downward coating apparatus. Some embodiments of this nature also involve an upward coating apparatus that is further along the path of substrate travel than the substrate cleaning device.

FIELD OF THE INVENTION

[0001] The present invention provides a coater in which coatings areapplied to substrates. Also provided are methods of depositing coatingson substrates. More specifically, the invention provides a coater andmethods in which thin films are applied to glass sheets or othersheet-like substrates.

BACKGROUND OF THE INVENTION

[0002] The bottom surface of a sheet-like substrate (e.g., a glasssheet) can be contaminated in situ (i.e., while the substrate is insidea coater) due to overspray from a downward coating operation. Forexample, when material is sputtered downwardly onto the top surface of asubstrate, some of the sputtered material can actually find its way ontothe substrate's bottom surface. This overspray phenomenon has been foundto leave unwanted coating on marginal portions of the substrate's bottomsurface. This can create an undesirable “picture frame” effect on thesubstrate. Thus, when a downward coating operation is performed on asubstrate, it would be desirable to provide means for cleaning (e.g.,removing any unwanted oversprayed coating from) the substrate's bottomsurface after the downward coating operation is performed. It would beparticularly desirable to provide in situ means (i.e., means inside acoater) for cleaning the bottom surface of a substrate after its topsurface has been coated by a downward coating operation.

[0003] Further, when a desired coating is applied to the bottom surfaceof a substrate by an upward coating operation after the top surface ofthe substrate has been coated by a downward coating operation, themarginal portions of the bottom surface can end up carrying both thedesired coating and unwanted overspray from the downward coatingoperation, while the central portion of this surface carries only thedesired coating. The resulting non-uniformity/picture frame effect, evenif not discernable with the naked eye, is undesirable in that it canthrow the coated substrate outside desired specifications. Thus, when adownward coating operation is performed prior to an upward coatingoperation, it would be particularly desirable to provide means forcleaning the bottom surface after the downward coating operation butbefore the upward coating operation.

[0004] Applying coating in an upward direction onto the bottom surfaceof a substrate can be highly advantageous. Upward coating operations canbe advantageously performed in a coater in addition, or as analternative, to downward coating operations. Particularly advantageousupward sputtering methods and equipment are described in U.S. patentapplications Ser. Nos. 09/868,542, 09/868,543, 09/979,314, 09/572,766,and 09/599,301, the entire contents of each of which are incorporatedherein by reference. In conjunction with upward coating technology, itwould be desirable to provide means for cleaning the bottom surface of asubstrate before (preferably shortly before) such surface is coated byan upward coating operation. It would be particularly desirable toprovide in situ means for cleaning the bottom surface of a substratebefore such surface is coated by an upward coating operation.

[0005] When a substrate is transported through a coater using asubstrate support, the substrate can be left with traces of contact fromthe support. Substrates are commonly conveyed through coaters usingspaced-apart transport rollers, such that the bottom surface of eachsubstrate is in direct contact with the rollers during conveyance. Therollers can leave traces of contact on the bottom surface of eachsubstrate. While these traces of contact tend to be relatively minor(and completely acceptable for many applications), it would be desirableto provide means for assuring that any such traces of contact arecompletely removed from the bottom surface of the substrate before suchsurface is coated by an upward coating operation.

[0006] It would be particularly desirable to perform an ion beamtreatment on the bottom surface of a substrate before applying aphotocatalytic coating to such surface by an upward coating operation.This is done in certain embodiments of the present invention, forexample, to facilitate depositing a high quality photocatalytic coating.This method is particularly preferred in embodiments wherein it isdesired to deposit a particularly thin high quality photocatalyticcoating.

SUMMARY OF THE INVENTION

[0007] In certain embodiments, the invention provides a coater adaptedfor applying coating onto a sheet-like substrate. The coater comprises asubstrate support defining a path of substrate travel extending throughthe coater. The coater also comprises an ion gun positioned beneath thepath of substrate travel and adapted for cleaning a bottom major surfaceof the substrate. In some embodiments, the coater further includes anupward coating apparatus positioned beneath the path of substrate travelat a location further along the path of substrate travel than the iongun. In one particular embodiment of this nature, the upward coatingapparatus is an upward sputtering apparatus that includes a lowersputtering target comprising a titanium-containing target material.

[0008] In certain embodiments, the invention provides a method ofprocessing a sheet-like substrate. The method comprises providing acoater adapted for applying coating onto the substrate. The coatercomprises a substrate support defining a path of substrate travelextending through the coater. The coater also comprises an ion gunpositioned beneath the path of substrate travel. The substrate isconveyed along the path of substrate travel and the ion gun is operatedto emit ions (e.g., upwardly) toward a bottom major surface of thesubstrate. The ions preferably comprise accelerated ions that form anion beam (e.g., a focused ion beam) and strike the bottom major surfaceof the substrate, thereby treating (e.g., cleaning) the substrate'sbottom major surface. In some embodiments, the coater further includesan upward coating apparatus positioned beneath the path of substratetravel at a location further along the path of substrate travel than theion gun. In one particular embodiment of this nature, the upward coatingapparatus is operated to apply a photocatalytic coating on thepreviously ion-treated bottom major surface of the substrate.

[0009] Certain embodiments of the invention provide a method ofprocessing a sheet-like substrate. In these embodiments, the methodcomprises providing a coater that is adapted for applying coating ontothe substrate. The coater comprises a substrate support defining a pathof substrate travel extending through the coater. A downward coatingapparatus is positioned in the coater above the path of substratetravel. An ion gun is positioned beneath the path of substrate travel.In the present embodiments, the ion gun is at a location further alongthe path of substrate travel than the downward coating apparatus(preferably, this ion gun is not vertically aligned with any downwardcoating apparatus). The method comprises conveying the substrate alongthe path of substrate travel, operating the downward coating apparatusto coat a top major surface of the substrate, and thereafter operatingthe ion gun to emit an ion beam toward a bottom major surface of thesubstrate. Here, the operation of the ion gun is performed to remove,substantially if not entirely, from the bottom major surface of thesubstrate any oversprayed coating that was inadvertently deposited uponmarginal portions of the bottom major surface of the substrate duringthe operation of the downward coating apparatus (in some cases, alsoshaving off some of the substrate material). In the present embodiments,the coater need not have any upward coating apparatus.

[0010] Certain embodiments of the invention provide a coater adapted forapplying coating onto a sheet-like substrate. In these embodiments, thecoater comprises a substrate support defining a path of substrate travelextending through the coater. A downward coating apparatus is positionedabove the path of substrate travel and is adapted for coating a topmajor surface of the substrate. An ion gun is positioned beneath thepath of substrate travel and is adapted for cleaning a bottom majorsurface of the substrate. In the present embodiments, the ion gun is ata location further along the path of substrate travel than the downwardcoating apparatus such that the ion gun is adapted to remove,substantially if not entirely, from the bottom major surface of thesubstrate oversprayed coating inadvertently deposited upon marginalportions of the bottom major surface of the substrate during operationof the downward coating apparatus. In the present embodiments, thecoater need not have any upward coating apparatus.

[0011] In certain embodiments, the invention provides a method ofprocessing a sheet-like substrate. In these embodiments, the methodcomprises providing a coater adapted for applying coating onto thesubstrate. The coater comprises a substrate support defining a path ofsubstrate travel extending through the coater. An ion gun is positionedbeneath the path of substrate travel. In the present embodiments, anupward coating apparatus is positioned beneath the path of substratetravel at a location further along the path of substrate travel than theion gun. The method comprises conveying the substrate along the path ofsubstrate travel, operating the ion gun to emit ions (e.g., an ion beam)toward a bottom major surface of the substrate (preferably such ionsform an ion beam comprising accelerated ions that strike the bottommajor surface of the substrate), and operating the upward coatingapparatus to deposit a photocatalytic coating on the bottom majorsurface of the substrate. In the present embodiments, the coater neednot have any downward coating apparatus.

[0012] Certain embodiments of the invention provide a coater adapted forapplying coating onto a sheet-like substrate. The coater comprises asubstrate support defining a path of substrate travel extending throughthe coater. An ion gun is positioned beneath the path of substratetravel. In these embodiments, an upward coating apparatus is positionedbeneath the path of substrate travel at a location further along thepath of substrate travel than the ion gun. In the present embodiments,the upward coating apparatus preferably comprises a titanium-containingsource material (e.g., a lower sputtering target comprising atitanium-containing target material). In the present embodiments, thecoater need not have any downward coating apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 illustrates a coater having disposed therein an ion gun inaccordance with certain embodiments of the present invention;

[0014]FIG. 2 illustrates a coater having disposed therein an ion gun andan upward coating apparatus in accordance with certain embodiments ofthe invention;

[0015]FIG. 3 illustrates a coater having disposed therein a downwardcoating apparatus, an ion gun, and an upward coating apparatus inaccordance with certain embodiments of the invention;

[0016]FIG. 4 illustrates another coater having disposed therein adownward coating apparatus, an ion gun, and an upward coating apparatusin accordance with certain embodiments of the invention;

[0017]FIG. 5 illustrates a further coater having disposed therein adownward coating apparatus, an ion gun, and an upward coating apparatusin accordance with certain embodiments of the invention; and

[0018]FIG. 6 illustrates a coater having disposed therein a downwardcoating apparatus and an ion gun in accordance with certain embodimentsof the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0019] The following detailed description is to be read with referenceto the drawings, in which like elements in different drawings have likereference numerals. The drawings, which are not necessarily to scale,depict selected embodiments and are not intended to limit the scope ofthe invention. Skilled artisans will recognize that the examplesprovided herein have many useful alternatives that fall within the scopeof the invention.

[0020] The present invention involves a coater 5 adapted for applyingcoating onto a sheet-like substrate 30. As shown in FIG. 1, the coater 5includes at least one chamber 10 in which a controlled environment canbe established. Preferably, the chamber is adapted for use in lowpressure deposition processes (e.g., in vacuum deposition processes).For example, the chamber 10 preferably is adapted for use at (e.g., isadapted for establishing and maintaining therein) a total gas pressureof less than about 140 torr., more preferably less than about 0.1 torr.,and perhaps most commonly between about 1 mtorr. and about 0.1 torr.(e.g., between about 1 mtorr. and about 30 mtorr.). Thus, in certainembodiments, the chamber 10 is adapted for use at (e.g., is providedwith conventional gas delivery and pumping systems adapted forestablishing and maintaining) pressures within any range or rangesdescribed in this paragraph.

[0021] The coater comprises one or more chambers. It will be apparent toskilled artisans that any desired number of chambers can be used. Insome cases, the coater comprises a series of connected chambers. Forexample, the coater may comprise a sputtering line. Sputtering lines arewell known in the present art. Briefly, a sputtering line comprises aseries of sputtering chambers aligned and connected such that sheet-likesubstrates (e.g., a plurality of spaced-apart substrates, such as glasssheets) supported horizontally on spaced-apart transport rollers can beconveyed sequentially through the chambers of the sputtering line.Typically, the sputtering line includes narrow evacuated tunnels, whichconnect adjacent chambers, through which the horizontally-orientedsubstrates are conveyed from one chamber to the next. Thus, substratesare typically conveyed sequentially through all of the chambers of asputtering line during sputtering. It will be appreciated that thepresent coater 5 may include a plurality of chambers aligned andconnected in this manner, regardless of the particular depositionprocesses that are performed in such chambers.

[0022] The present coater 5 can include chambers adapted for carryingout different deposition processes. For example, the coater can includeone or more chambers in which sputtering is performed and one or morechambers in which evaporation is performed. Further, the coater caninclude one or more chambers in which sputtering is performed and one ormore chambers in which chemical vapor deposition is performed.Similarly, the coater can include one or more chambers in whichsputtering is performed and one or more chambers in which ion beamcoating deposition is performed. Still further, the coater can includeone or more chambers in which chemical vapor deposition is performed andone or more chambers in which evaporation is performed. Variousalternatives of this nature will be apparent to skilled artisans giventhe present teaching as a guide.

[0023] A variety of substrates are suitable for use in the presentinvention. In most cases, the substrate is a sheet of transparentmaterial (i.e., a transparent sheet). However, the substrate is notrequired to be transparent. For example, opaque substrates may be usefulin some cases. However, it is anticipated that for most applications,the substrate will comprise a transparent or translucent material, suchas glass or clear plastic. In many cases, the substrate will be a glasssheet. A variety of known glass types can be used, and soda-lime glassis expected to be preferred.

[0024] Substrates of various size can be used in the present invention.An advantage of the coater 5 is that it can be used to processlarge-area substrates. Certain embodiments involve a substrate having awidth of at least about 0.5 meter, preferably at least about 1 meter,perhaps more preferably at least about 1.5 meters (e.g., between about 2meters and about 4 meters), and in some cases at least about 3 meters.

[0025] Substrates of various thickness can be used in the presentinvention. Commonly, substrates with a thickness of about 1-5 mm areused. Some embodiments involve a substrate with a thickness of betweenabout 2.3 mm and about 4.8 mm, and perhaps more preferably between about2.5 mm and about 4.8 mm. In some cases, a sheet of glass (e.g.,soda-lime glass) with a thickness of about 3 mm is used.

[0026] The coater 5 comprises a substrate support 40 defining a path ofsubstrate travel 60 extending through the coater. Preferably, the pathof substrate travel extends substantially horizontally through thecoater. In the embodiments of FIGS. 1-3, the substrate support 40defines a path of substrate travel 60 extending through the coater 5between a chamber inlet 15 and a chamber outlet 20. In embodimentswherein the coater 5 comprises more than one chamber, the chambers aretypically connected such that the path of substrate travel 60 extendsthrough each of the chambers between a coater inlet and a coater outlet.

[0027] Preferably, the substrate support 40 is configured formaintaining (e.g., supporting) the substrate in a horizontalconfiguration while the substrate is being coated (e.g., duringconveyance of the substrate through the coater). Thus, the support 40desirably is adapted to convey a sheet-like substrate 30, and preferablymultiple sheet-like substrates that are spaced-apart from one another,through the coater while maintaining the/each substrate 30 in ahorizontal orientation (e.g., wherein a top major surface 14 of the/eachsubstrate 30 is upwardly oriented while a bottom major surface 12 ofthe/each substrate 30 is downwardly oriented). In the embodiments shownin the present figures, the substrate support 40 comprises a pluralityof spaced-apart transport rollers 310. Typically, at least one of therollers is rotated (e.g., by energizing a motor operably connected tothe roller) such that the substrate 30 is conveyed through the chamber10 along the path of substrate travel 60. When the substrate is conveyedover such rollers, the bottom surface 12 of the substrate 30 is indirect physical (i.e., supportive) contact with the rollers. Thesubstrate is typically conveyed through the coater at a speed of about100-500 inches per minute. In FIGS. 3-6, embodiments are illustratedwherein the substrate is a sheet of glass that is on the substratesupport during conveyance, and wherein other sheets of glass are also onthe substrate support, such sheets of glass being spaced-apart from oneanother on the substrate support and conveyed in such a spaced-apartconfiguration. While the illustrated substrate support 40 comprises aplurality of spaced-apart rollers 310, it is to be appreciated thatother types of substrate supports can be used.

[0028] In embodiments wherein the substrate support 40 is formed bytransport rollers, the rollers can be of any conventional structure. Ithas been found that good results can be obtained by employingcylindrical (e.g., aluminum) rollers about which a rope is spirallywound, with such rope providing the surface with which the substrate isin direct contact. The rope can be formed of Kevlar™, i.e.,poly-para-phenylene terephthalamide, or another polymer (e.g.,nylon-like polymer). Preferably, a high melting point polymer is used(e.g., a polymer having a melting point above the maximum processingtemperature established in a desired deposition process, e.g., at leastabout 165 degrees C., more preferably at least about 200 degrees C., andperhaps optimally at least about 400 degrees C.). Rollers carrying aspirally-wound rope (or a plurality of individual bands) areparticularly desirable for embodiments wherein an upward coating processis performed, as the rope reduces the area of contact between therollers and the substrate and thus provides a particularly non-damagingsupport for the substrate's freshly-coated bottom surface. Thus, incertain embodiments, the substrate support 60 comprises a plurality ofspaced-apart rollers each having at least one rope disposed about theroller.

[0029] In the embodiment of FIG. 1, an ion gun 50 is positioned beneath(i.e., at a lower elevation than) the path of substrate travel 60. Theion gun preferably is disposed within (i.e., inside) the coater 5. Forexample, the ion gun 50 can be disposed within a chamber 10 of thecoater 5 that is adapted for use at a total gas pressure of less thanabout 140 torr., more preferably less than about 0.1 torr., and perhapsmost commonly between about 1 mtorr. and about 0.1 torr. (e.g., betweenabout 1 mtorr. and about 30 mtorr.). The ion gun 50 can be mountedwithin such a chamber 10 by any conventional means (e.g., using anyconvention mounting hardware). For example, the ion gun can be securedto a flange or flanges extending from a floor and/or sidewall of thecoater.

[0030] The mounted ion gun preferably is adapted for treating (e.g., foraccelerating ions at) the bottom surface of the substrate 30 as it isconveyed along the path of substrate travel 60. Thus, the mounted iongun preferably is positioned beneath the path of substrate travel 60,such that when the ion gun 50 is operated it emits (e.g., upwardlybetween two spaced-apart transport rollers) ions, preferably a beam ofions, toward the bottom major surface 12 of the substrate 30. It will beappreciated that the ion gun 50 will typically be operated when thesubstrate 30 is on the support 40 at a portion of the path of substratetravel 60 adjacent (e.g., directly above) the ion gun.

[0031] The ion gun 50 desirably is adapted for emitting ions that span(e.g., an ion beam that spans) substantially the entire width(preferably the entire width) of the substrate 30. For example, the iongun preferably emits a curtain-like ion beam that spans the entire widthof the substrate's bottom major surface 12. Thus, the ion gun 50preferably is adapted for treating (e.g., cleaning) the entire bottomsurface 12 of the substrate 30. This can be accomplished in severalways. One way is by providing a single ion gun (which may have one ionsource or multiple ion sources) that is capable of generating an ionbeam or beams spanning substantially the entire width (preferably theentire width) of the substrate. Another way is to provide a plurality ofion guns, which together generate a collective ion beam or beamsspanning substantially the entire width of the substrate. For example,two or more ion guns can be configured and operated such that theircombined beams span the entire width of the substrate.

[0032] The invention is particularly advantageous in processing largearea substrates, such as glass sheets for architectural and automotiveglass applications. Substrates of this nature commonly have a width ofat least about .5 meter, more commonly at least about one meter, andtypically greater than about 1.5 meters (e.g., between about 2 metersand about 4 meters). Accordingly, the ion gun 50 is preferably adaptedto emit an ion beam that spans the entire width of such a substrate(i.e., a substrate having a width in one or more of these ranges). Withlarge area substrates in particular (especially those formed of glass),it is desirable to convey the substrates through the coater in ahorizontal orientation, rather than in a vertical orientation.

[0033] The ion gun 50 can be any ion source. In certain preferredembodiments, the ion gun is adapted to ionize gas molecules and thenfocus, accelerate, and emit them as a narrow beam (i.e., as an ionbeam). For example, the ion gun can be a linear ion source. The ion gun,however, is by no means required to emit ions in the form of a beam.Some ion guns are not operable in low pressure environments (e.g., undervacuum conditions). The present ion gun 50, however, preferably isoperable in low pressure environments (e.g., in a vacuum depositionchamber). For example, the ion gun 50 is preferably adapted to operatein environments having a total gas pressure of less than about 140torr., more preferably less than about 0.1 torr., and perhaps mostcommonly between about 1 mtorr. and about 0.1 torr. (e.g., between about1 mtorr. and about 30 mtorr.).

[0034] The present ion gun is preferably one that accelerates ionselectrodynamically, rather than electrostatically. The use ofelectrostatic fields to transfer, collect, or manipulate ions is wellknown. Typically, electrostatic fields are used with ion guns thatoperate at or near atmospheric pressure. Electrostatic fields tend to beless desirable for ion guns that operate in low pressure environments(e.g., under vacuum). To the contrary, electrodynamic fields are moreeffective for accelerating ions in low pressure environments. In certainpreferred embodiments, therefore, the ion gun comprises an ion sourcethat accelerates ions electrodynamically.

[0035] In certain particularly preferred embodiments, the ion gun 50 isan anode layer ion source. Anode layer ion sources accelerate ionselectrodynamically, rather than electrostatically. As a result, they aredesirable for use in low pressure environments. Further, anode layer ionsources are compatible with a wide variety of working gases, includingargon, oxygen, nitrogen, hydrocarbons, and mixtures of such gases.Suitable ion sources of this nature are commercially available fromVeeco (Ft. Collins, Colo., USA) under the trade names ALS 106C, ALS144L, ALS 340L, ALS 340W. Reference is made to U.S. Pat. No. 6,147,354(Maishev et al.), the entire contents of which are incorporated hereinby reference, in which there is described operation of an anode-layertype ion source in a vacuum chamber.

[0036] With continued reference to FIG. 1, it can be appreciated thatthe ion gun 50 is disposed within the coater 5. As noted above, the iongun 50 may be provided (e.g., mounted) in a chamber 10 of the coater 5that is adapted for use at a total gas pressure of less than about 140torr., more preferably less than about 0.1 torr., and perhaps mostcommonly between about 1 mtorr. and about 0.1 torr. (e.g., between about1 mtorr. and about 30 mtorr.).

[0037] In embodiments wherein the substrate support 40 is provided inthe form of spaced-apart transport rollers 310, the spacing of therollers 310 is preferably kept fairly small to permit small substratesto be processed without any significant risk of having the substratesfall between the spaced-apart rollers. The maximum safe spacing ispreferably determined on a case-by-case basis for a desired range ofsubstrate sizes.

[0038] The ion gun 50 and the rollers 310 preferably are configured suchthat the ion gun 50 is adapted to emit an ion beam upwardly between anadjacent pair of the rollers (this pair of rollers preferably isgenerally above the ion gun). It can be appreciated that there is a gap45 between these two rollers. If so desired, this pair of rollers can bespaced further apart than other rollers in the coater 5, such that thisparticular gap 45 is wider than other such gaps in the coater. This maybe done to minimize any interference of the rollers with the ion beam.

[0039] Thus, in certain embodiments the ion gun 50 is positioned beneatha portion of the path of substrate travel 60 where an adjacent pair ofrollers are mounted further apart than other adjacent rollers in thecoater. In such embodiments, there is a gap 45 between the two rollersgenerally above/over the ion gun 50 that is wider than the gaps betweenother adjacent roller pairs in the coater 5. In such embodiments, therollers in other areas of the chamber 10 can have conventional spacing.

[0040] It may also be desirable if certain rollers in the chamber 10 areremovable, such that the chamber 10 can be readily converted between afirst configuration, wherein a particularly wide gap 45 is providedbetween the two transport rollers nearest the ion gun, and a secondconfiguration having a conventional roller arrangement wherein all ofthe rollers are evenly spaced.

[0041] Instead of mounting the rollers above the ion gun 50 furtherapart, these rollers could instead be made smaller in diameter.Conventional transport rollers are hollow metal tubes. If so desired,particularly small diameter tubes could be used. In such cases, it maybe desirable to stiffen the rollers, e.g., by filling them with rigidfoam. In order to maintain the same transport speed of a substrate alongthe support 60, these small-diameter rollers could be rotated morerapidly, e.g., by means of a pair of gears having an appropriate gearratio. In one embodiment, the two rollers between which the ion gun 50emits ions are smaller (i.e., have a smaller diameter) than otherrollers in the coater. While the foregoing embodiments are expected tobe advantageous, it is to be understood that the ion gun 50 can simplybe aligned beneath a gap that results from conventional roller spacing.

[0042] As can be appreciated with reference to FIGS. 2-5, the coater 5in certain embodiments includes an upward coating apparatus 55. Whenprovided, the upward coating apparatus 55 is adapted for coating thebottom major surface 12 of the substrate 30. In embodiments of thisnature, the ion gun 50 and the upward coating apparatus 55 arepreferably both disposed (e.g., mounted) within the coater 5. If sodesired, the ion gun 50 and an upward coating apparatus 55 can both bedisposed in a common chamber (i.e., in the same chamber) of the coater5. This, however, is by no means required. The ion gun 50 and the upwardcoating apparatus 55, when it 55 is provided, are preferably bothpositioned beneath (i.e., at a lower elevation than) the path ofsubstrate travel 60.

[0043] In certain particularly advantageous embodiments, an upwardcoating apparatus 55 is positioned (e.g., mounted) at a location furtheralong the path of the substrate travel 60 than the ion gun 50. Bypositioning an upward coating apparatus 55 at a location further alongthe path of substrate travel 60 than the ion gun 50, the ion gun isadapted for treating (e.g., cleaning) the bottom major surface 12 of thesubstrate 30 before the upward coating apparatus is operated to coat thebottom major surface of the substrate.

[0044] When provided, the upward coating apparatus 55 is preferablypositioned beneath a gap 145 between an adjacent pair of transportrollers 310. This gap 145 may result from conventional roller spacing.Alternatively, this gap 145 may be wider than the gaps between otheradjacent roller pairs in the coater 5. This can be accomplished in themanner described above with reference to the transport rollers over theion gun (i.e., by mounting the rollers that define this gap 145 furtherapart and/or by decreasing the size of these rollers).

[0045] When provided, the upward coating apparatus 55 can be any type ofupward coating apparatus. For example, this upward coating apparatus 55can be a sputter coating apparatus, an ion beam coating depositionapparatus, an evaporation coating apparatus, a chemical vapor depositionapparatus, or any other apparatus that is adapted for performing anupward coating operation.

[0046] In certain preferred embodiments, the optional upward coatingapparatus 55 is an upward sputtering apparatus. For example, thisapparatus 55 may include a lower sputtering target 360, 360 a, 360 bpositioned beneath the path of substrate travel. This upward coatingapparatus may include a lower gas distribution system (e.g., comprisingat least one gas-delivery outlet) adapted for delivering sputtering gasto the lower region of the coater (i.e., the region of the coater belowthe path of substrate travel). This is perhaps best appreciated withreference to FIGS. 4 and 5, wherein the illustrated coaters includelower sputtering targets 360 a, 360 b and lower gas distribution pipes375 adjacent the lower targets. Also shown in FIGS. 4 and 5 are optionallower anodes 370, which preferably are below the path of substratetravel. When provided, the lower anodes 370 are typically positionedadjacent the lower targets 360, 360 a, 360 b. Upward sputtering systemsare described in U.S. patent applications Ser. Nos. 09/868,542,09/868,543, 09/979,314, 09/572,766, and 09/599,301.

[0047] In other embodiments, the optional upward coating apparatus 55 isan evaporation coating apparatus. An apparatus 55 of this naturetypically comprises a source of coating material to be evaporated. Thissource material will typically be positioned beneath the path ofsubstrate travel 60. The source material can be provided in the form ofa boat, crucible, strip, or coil that contains, or is formed of, thedesired source material. Means are also typically provided fordelivering energy to such source material. For example, the sourcematerial may be provided in conjunction with a heat source adapted forheating such material by direct or indirect resistance, by thermalconduction, by radiation or induction, by electron beam, or by laserirradiation or arcing.

[0048] Various processes for coating substrates by evaporation are knownin the art. Briefly, evaporation is a form of physical vapor depositionthat involves delivering energy to a source material in vacuum until itevaporates at adequate rates. The source material is transported inresidual gas phase to the substrate, where such gas phase materialcondenses upon the substrate and forms the desired coating. When theoptional upward coating apparatus 55 is an evaporation apparatus, it maybe desirable to maintain the chamber at pressures on the order ofbetween about 10⁻⁶ mbar. and about 10⁻⁴ mbar.

[0049] In other embodiments, the optional upward coating apparatus 55 isa chemical vapor deposition (i.e., CVD) apparatus. An apparatus of thisnature typically comprises a gas outlet for delivering precursor gas tothe lower region of the coater. Preferably, this gas outlet ispositioned below the path of the substrate travel 60, such that from theprecursor gas, coating material condenses upon the bottom surface of thesubstrate 30. A CVD apparatus of this nature will typically comprise agas supply from which the precursor gas is delivered through the gasoutlet and into the lower region of the coater. Any known CVD apparatuscan be used. If so desired, this upward coating apparatus can be aplasma-enhanced chemical vapor deposition apparatus of the typedescribed in U.S. patent application Ser. No. 10/373,703, entitled“Plasma-Enhanced Film Deposition” (Hartig), filed on Dec. 18, 2002.

[0050] In certain embodiments, the upward coating apparatus 55 comprisesan ion gun. This ion gun can be part of any known ion-assisteddeposition (i.e., IAD) process. For example, this ion gun can be part ofan ion beam sputter deposition source comprising a sputtering targetagainst which this ion gun accelerates ions, such that atoms of thetarget material are ejected from the target upwardly toward thesubstrate. Alternatively, this ion gun can be part of an ion-assistedevaporation apparatus, such as those disclosed in the publication“Ion-Based Methods For Optical Thin Film Deposition” (Journal ofMaterial Science; J. P. Marting, 21 (1986) 1-25), the entire teachingsof which are incorporated herein by reference. These types of IADmethods are known in the art, as are various other suitable IAD methods.

[0051] In certain embodiments, the coater 5 comprises a downward coatingapparatus 65 that is adapted for coating a top major surface 14 of thesubstrate 30. Embodiments of this nature are exemplified in FIGS. 3-6.In such embodiments, the ion gun 50 is preferably positioned (e.g.,mounted) at a location further along the path of substrate travel 60than the downward coating apparatus 65. The ion gun 50 is thus adaptedfor removing, substantially if not entirely, from the bottom majorsurface of the substrate oversprayed coating that has been inadvertentlydeposited upon marginal portions of the bottom major surface of thesubstrate during operation of the downward coating apparatus. In thepresent embodiments (which involve a downward coating apparatus,together with an ion gun positioned below the path of substrate travelat a location further along the path of substrate travel than thedownward coating apparatus), no upward coating apparatus is required inthe coater. However, in FIGS. 3-5, an optional upward coating apparatus55 is positioned at a location further along the path of substratetravel 60 than the ion gun 50. Thus, any oversprayed coating on thebottom surface 12 of the substrate 30 can be substantially, if notentirely, removed before this surface 12 is coated during operation ofthe optional upward coating apparatus 55.

[0052] When provided, the downward coating apparatus 65 can be any typeof downward coating apparatus. In certain preferred embodiments, thedownward coating apparatus 65 is a downward sputtering apparatus. Insuch embodiments, the downward sputtering apparatus comprises an uppersputtering target 320, 320 c, 320 d, 320 e, 320 f positioned above thepath of substrate travel 60. Conjointly, the coater can be provided withupper gas distribution pipes 335 (e.g., having outlets that are)positioned above the path of substrate travel 60. It will typically bepreferred to also provide upper anodes 330 above the path of substratetravel 60. When provided, the upper anodes 330 are preferably positionedadjacent upper targets. As noted above, each target in FIGS. 2-6 isdepicted as being a cylindrical target, although planar targets can beused as well.

[0053] In other embodiments, the optional downward coating apparatus 65comprises a chemical vapor deposition apparatus. Such an apparatus maycomprises a gas delivery outlet for delivering precursor gas to theupper region of the coater (i.e., the region of the coater above thepath of substrate travel). Preferably, this gas outlet is positionedabove the path of substrate travel 60, such that from the precursor gas,coating material condenses upon the top major surface 14 of thesubstrate 30. A CVD apparatus of this nature will typically comprise agas supply from which the precursor gas is delivered through the gasoutlet and into the upper region of the coater. If so desired, thisdownward coating apparatus can be a plasma-enhanced chemical vapordeposition apparatus of the type described in U.S. patent applicationSer. No. 10/373,703, entitled “Plasma-Enhanced Film Deposition”(Hartig), filed on Dec. 18, 2002.

[0054] In certain embodiments, the downward coating apparatus comprisesan upper ion gun. This upper ion gun can be part of any desired downwardion-assisted deposition process. For example, this upper ion gun can bepart of an ion beam sputter deposition source comprising a sputteringtarget against which this ion gun accelerates ions, such that atoms ofthe target material are ejected from the target downwardly toward thesubstrate. This type of IAD method is known in the art, as are variousother suitable IAD methods.

[0055] It has been discovered that the bottom surface of a substrate canbe coated inadvertently due to overspray from a downward coatingoperation. For example, when material is sputtered downwardly onto thetop surface of a substrate, some of the sputtered material can actuallyfind its way onto the bottom surface of the substrate. This phenomenonhas been found to leave unwanted coating on marginal portions of thesubstrate's bottom surface. This can create an undesirable picture frameeffect on the substrate. Further, if a desired coating is subsequentlyapplied to the bottom surface by an upward coating operation, themarginal portions of this surface will end up carrying both the desiredcoating and the unwanted oversprayed coating, while the central portionof this surface carries only the desired coating. Thisnon-uniformity/picture frame effect can have a variety of adverseeffects on the intended coating properties/the desired specifications.

[0056] These particular overspray problems can be eliminated bypositioning the ion gun 50 further along the path of substrate travel 60(preferably at a location beyond where the substrate is exposed to filmdeposition from the downward coating apparatus) than the downwardcoating apparatus 65. This enables the ion gun 50 to remove from thebottom surface 12 of the substrate 30 oversprayed coating (in somecases, the ion gun is operated so it also mills away a small thicknessof glass from the bottom surface of a glass substrate) that has beeninadvertently deposited on marginal portions of the substrate's bottomsurface 12 during operation of the downward coating apparatus 65. Thisalso tends to substantially reduce, if not eliminate, any traces ofcontact on the substrate's bottom surface that may have resulted fromconveying the substrate through the coater on the substrate support. Ifan upward coating apparatus 55 is also provided, it is preferablylocated further along the path of substrate travel 60 than the ion gun50. This enables the ion gun 50 to remove (substantially if notentirely) from the bottom surface 12 of the substrate 30 oversprayedcoating that has been inadvertently deposited on marginal portions ofthe substrate's bottom surface 12 during operation of the downwardcoating apparatus 65 before this surface 12 is coated during operationof the upward coating apparatus 55.

[0057] It has also been discovered that a further overspray problem canresult when coating is applied upwardly onto the bottom surface 12 of asubstrate 30 before coating is applied downwardly onto the top surface14 of the substrate 30. In particular, the desired coating properties onthe substrate's bottom surface 12 can be compromised when material fromthe downward coating operation oversprays the coating that haspreviously been applied upwardly onto the substrate's bottom surface 12.Even if such oversprayed material has no apparent (e.g., readily visibleto the naked eye) effect on the coated substrate, it can compromise thedesired properties of the coated substrate. This can be particularlyproblematic when the substrate's bottom surface is intended to haveparticular surface properties (e.g., when the substrate's bottom surfaceis intended to carry a surface-effect coating), such as photoactivity,hydrophilicity, hydrophobicity, or the like. The oversprayed coating onthe substrate's bottom surface may nullify or reduce such intendedsurface properties.

[0058] To obviate this problem, the upward coating apparatus 55 canoptionally be disposed in a final chamber (in some cases, in the finaldeposition zone of the final chamber) of the coater. This final chambermay be the last chamber along the path of substrate travel 60.Alternatively, this final chamber may be the last operating chamber(i.e., the last chamber in which any film deposition operation isperformed) along the path of substrate travel. In such cases, the coatermay include one or more non-operated chambers further along the path ofsubstrate travel. The inventors have discovered these embodiments to beadvantageous in that once this upward coating apparatus is operated toapply a desired coating on the bottom major surface of the substrate,this desired coating will not be subjected to any subsequent overspray,such as may otherwise occur if the thus-coated substrate weresubsequently conveyed into an active (i.e., operated) downward coatingzone. Thus, in certain embodiments, operation of the upward coatingapparatus is performed after all other coating of the substrate in thecoater has been performed. Similarly, in certain embodiments, thesubstrate is not conveyed beneath any operating/operated downwardcoating apparatus in the coater after the operation of the upwardcoating apparatus, such that marginal portions of coating applied to thebottom major surface of the substrate will not be concealed byoversprayed coating from any subsequent downward coating apparatus inthe coater.

[0059] In certain embodiments wherein an upward coating apparatus isprovided, the coater 5 is operated so as to deposit upon the bottommajor surface of the substrate a coating (which in some cases comprisesat least some high index film having a refractive index of at leastabout 2.3) having a total optical thickness of less than about 690 Å. Inthese embodiments, any traces of contact left on this coating from thesubstrate support will tend to be invisible or at least very difficultto perceive. In some embodiments of this nature, the coater 5 isoperated such that the top major surface of the substrate is also coatedwith a coating, preferably with one having a total optical thickness ofat least about 1,000 Å. In certain embodiments of this nature, whereinthe coater has at least one upward coating apparatus and a plurality ofdownward coating apparatuses, the coater is operated to deposit alow-emissivity coating on the top major surface of the substrate and todeposit a surface-effect coating on the bottom major surface of thesubstrate. Here, the surface-effect coating is preferably selected fromthe group consisting of a photocatalytic coating, a hydrophilic coating,and a hydrophobic coating. In some embodiments of this nature, thesurface-effect coating comprises titanium oxide and/or silicon oxide. Inone such embodiment, the surface-effect coating is a photocatalyticcoating comprising titanium oxide.

[0060] Low-emissivity coatings are well known in the art and typicallyinclude at least one region of infrared-reflective film sandwichedbetween at least two regions of transparent dielectric film. Theinfrared-reflective film, which typically comprises a conductive metalsuch as silver, gold, or copper, reduces the transmission of radiantheat through the coating. The transparent dielectric film is usedprimarily to reduce visible reflectance and to control other propertiesof the coatings, such as color. Commonly used transparent dielectricsinclude oxides of zinc, tin, indium, bismuth, and titanium, and alloysand mixtures thereof, as well as certain nitrides (e.g., siliconnitride). Useful low-emissivity coatings are described in U.S. patentapplication Ser. No. 09/728,435, the entire teachings of which areincorporated herein by reference.

[0061] Photocatalytic coatings typically comprise a semiconductor thatcan absorb ultraviolet radiation and can photocatalytically degradeorganic materials such as oil, plant matter, fats, and greases. The mostpowerful of the photocatalysts appears to be titanium oxide (e.g.,titanium dioxide). Useful photocatalytic coatings are described in U.S.Pat. No. 5,874,701 (Watanabe et al), U.S. Pat. No. 5,853,866 (Watanabeet al), U.S. Pat. No. 5,961,843 (Hayakawa et al.), U.S. Pat. No.6,139,803 (Watanabe et al), U.S. Pat. No. 6,191,062 (Hayakawa et al.),U.S. Pat. No. 5,939,194 (Hashimoto et al.), U.S. Pat. No. 6,013,372(Hayakawa et al.), U.S. Pat. No. 6,090,489 (Hayakawa et al.), U.S. Pat.No. 6,210,779 (Watanabe et al), U.S. Pat. No. 6,165,256 (Hayakawa etal.), and U.S. Pat. No. 5,616,532 (Heller et al.), the entire contentsof each of which are incorporated herein by reference.

[0062] Hydrophilic coatings have an affinity for water and tend to causewater applied to such coatings to sheet. Useful hydrophilic coatings aredescribed in U.S. patent applications Ser. Nos. 09/868,542, 09/868,543,09/599,301, and 09/572,766, the entire contents of each of which areincorporated herein by reference.

[0063] Hydrophobic coatings are applied to glass to repel water, thuscausing water on such coatings to bead up, rather than spreading into asheet. Useful hydrophobic coatings are described in U.S. Pat. No.5,424,130, issued to Nakanishi, et al., the entire teachings of whichare incorporated herein by reference.

[0064] As noted above, the invention provides certain embodimentswherein the coater includes an upward coating apparatus that ispositioned beneath the path of substrate travel at a location furtheralong the path of substrate travel than the ion gun. In some suchembodiments, the invention comprises operating the upward coatingapparatus to coat the bottom major surface of the substrate after theion gun has been operated to treat the bottom major surface of thesubstrate. In some embodiments of this nature, operation of the upwardcoating apparatus comprises depositing on the bottom major surface ofthe substrate a surface-effect coating selected from the groupconsisting of a photocatalytic coating, a hydrophilic coating, and ahydrophobic coating. In these embodiments, the coater need not have anydownward coating apparatus. In some cases, the surface-effect coatingcomprises titanium oxide and/or silicon oxide. For example, thesurface-effect coating in one such case is a photocatalytic coatingcomprising titanium oxide.

[0065] Thus, in certain embodiments, an upward coating apparatus 55 inthe coater 5 is adapted for depositing a high quality photocatalyticcoating onto the bottom surface 12 of the substrate 30 after ionbombarding this surface 12 using a preceding ion gun 50. In theseembodiments, the upward coating apparatus 55 that is adapted fordepositing the photocatalytic coating onto the bottom surface 12 of thesubstrate 30 is located further along the path of substrate travel thanthe ion gun 50. In certain preferred embodiments, a particularly thinhigh quality photocatalytic coating is deposited on the bottom surfaceof the substrate using this upward coating apparatus after the bottomsurface has been ion treated using the ion gun 50. In these embodiments,the thin high quality photocatalytic film preferably is deposited at atotal optical thickness of less than about 690 Å.

[0066] Thus, in certain embodiments, the optional upward coatingapparatus 55 is adapted for applying a photocatalytic coating. In someembodiments of this nature, the upward coating apparatus 55 is adaptedfor applying a photocatalytic coating that comprises (perhaps morepreferably consists essentially of, and perhaps optimally consists of)titanium oxide. In these embodiments, the upward coating apparatusdesirably comprises a source or sources of titanium and oxygen. Forexample, the upward coating apparatus 55 can optionally include a lowersputtering target comprising titanium (e.g., metallic titanium ortitanium oxide). Conjointly, the lower region of the coater adjacentsuch target can optionally be provided with an oxidizing atmosphere.With photocatalytic titanium oxide coatings and other high indexphotocatalysts in particular, it is especially desirable not to subjectsuch coatings to subsequent overspraying, as overspray on such coatingswill tend to be more visible than overspray on other types of coatings,due to the somewhat reflective nature of these coatings.

[0067] In certain advantageous embodiments, the optional upward coatingapparatus 55 comprises a lower sputtering target of the nature describedin U.S. patent application Ser. No. 60/262,878, the entire teachings ofwhich are incorporated herein by reference.

[0068] If a photocatalytic coating applied to the bottom major surfaceof a substrate is subjected to overspray from a subsequent downwardcoating operation, the desired photocatalytic properties can bejeopardized. Thus, in embodiments wherein a photocatalytic coating isapplied to the bottom major surface of a substrate by an upward coatingoperation, this upward coating operation is desirably not followed byany subsequent downward coating operation in the coater.

[0069] In embodiments of the invention wherein one apparatus (e.g., anion gun or a coating apparatus) is at a location further along the pathof substrate travel than another apparatus (e.g., an ion gun or acoating apparatus), these apparatuses are of course not verticallyaligned directly above/below each another. Preferably, though notnecessarily, they are in separate deposition zones (which may beisolated from each other by gas separation and/or a curtain, wall, orother divider), and in some cases they are in separate chambers of thecoater. The term “titanium-containing” material refers to any materialthat includes at least some titanium (the same convention is used forother materials). When the ion gun 50 is used to clean the bottomsurface of the substrate, argon or another inert gas is preferably usedfor the cleaning (i.e., Ar gas is used in the ion gun to accelerate Ar+ions toward the substrate's bottom surface). In some cases, the ion gunwhen used to clean the bottom surface of the substrate is operated toproduce an ion beam having an ion energy of between about 300 eV andabout 5,000 eV, perhaps more preferably between about 1,500 eV and about2,000 eV, and perhaps optimally between about 1,400 eV and about 1,600eV. Preferably, the ion gun is operated to produce an ion bean thatimpinges the substrate's bottom surface at an angle of about 90 degrees,or elsewhere within a range of between about 30 and about 90 degrees. Incertain embodiments, the substrate is fully processed (e.g., both of itsmajor surfaces can be coated) in a single pass through the coater 5.

[0070] While there have been described what are believed to be preferredembodiments of the present invention, those skilled in the art willrecognize that other and further changes and modifications can be madewithout departing from the spirit of the invention, and all such changesand modifications should be understood to fall within the scope of theinvention.

What is claimed is:
 1. A method of processing a sheet-like substrate,the method comprising: a) providing a coater adapted for applyingcoating onto the substrate, the coater comprising a substrate supportdefining a path of substrate travel extending through the coater, adownward coating apparatus positioned above the path of substratetravel, and an ion gun positioned beneath the path of substrate travel,wherein the ion gun is at a location further along the path of substratetravel than the downward coating apparatus; b) conveying the substratealong the path of substrate travel; c) operating the downward coatingapparatus to coat a top major surface of the substrate; and d) operatingthe ion gun to emit an ion beam toward a bottom major surface of thesubstrate, said operation of the ion gun being performed to remove fromthe bottom major surface of the substrate any oversprayed coating thatwas inadvertently deposited upon marginal portions of the bottom majorsurface of the substrate during said operation of the downward coatingapparatus.
 2. The method of claim 1 wherein the substrate is maintainedin a horizontal orientation during said conveyance of the substratealong the path of substrate travel.
 3. The method of claim 1 wherein thesubstrate is a sheet of glass that is on the substrate support duringsaid conveyance, and wherein other sheets of glass are also on thesubstrate support, such sheets of glass being spaced-apart from oneanother on the substrate support and conveyed in such a spaced-apartconfiguration.
 4. The method of claim 1 wherein the substrate supportcomprises a plurality of spaced-apart transport rollers, the methodcomprising rotating at least one of the transport rollers to achievesaid conveyance of the substrate along the path of substrate travel. 5.The method of claim 4 wherein said operation of the ion gun emits saidion beam upwardly between an adjacent pair of the spaced-apart transportrollers.
 6. The method of claim 1 wherein the downward coating apparatusis a downward sputtering apparatus comprising an upper sputtering targetpositioned above the path of substrate travel, and wherein saidoperation of the downward coating apparatus comprises establishing aplasma adjacent said upper sputtering target.
 7. The method of claim 1wherein the downward coating apparatus is a chemical vapor depositionapparatus, and wherein said operation of the downward coating apparatuscomprises delivering precursor gas to an upper region of the coater. 8.The method of claim 1 wherein the downward coating apparatus comprisesan upper ion gun, the upper ion gun being adapted for ion beam coatingdeposition, and wherein said operation of the downward coating apparatuscomprises operating the upper ion gun to emit an ion beam toward the topmajor surface of the substrate.
 9. The method of claim 1 furthercomprising an upward coating apparatus, the upward coating apparatusbeing positioned beneath the path of substrate travel at a locationfurther along the path of substrate travel than the ion gun, the methodcomprising operating the upward coating apparatus to coat the bottommajor surface of the substrate after said operation of said ion gun hasremoved any oversprayed coating from the bottom major surface of thesubstrate.
 10. The method of claim 9 wherein said operation of theupward coating apparatus is performed after all other coating of thesubstrate in the coater has been performed.
 11. The method of claim 9wherein the substrate is not conveyed beneath any operating downwardcoating apparatus in the coater after said operation of the upwardcoating apparatus, such that marginal portions of coating applied to thebottom major surface of the substrate will not be concealed byoversprayed coating from any subsequent downward coating apparatus inthe coater.
 12. The method of claim 9 wherein said operation of theupward coating apparatus is performed in a final chamber of the coater.13. The method of claim 9 wherein the bottom major surface of thesubstrate is coated with a coating having a total optical thickness ofless than about 690 Å.
 14. The method of claim 13 wherein the top majorsurface of the substrate is coated with a coating having a total opticalthickness of at least about 1,000 Å.
 15. The method of claim 9 whereinsaid operation of the upward coating apparatus comprises depositing onthe bottom major surface of the substrate a surface-effect coatingselected from the group consisting of a photocatalytic coating, ahydrophilic coating, and a hydrophobic coating.
 16. The method of claim15 wherein the surface-effect coating comprises titanium oxide and/orsilicon oxide.
 17. The method of claim 16 wherein the surface-effectcoating is a photocatalytic coating comprising titanium oxide.
 18. Themethod of claim 9 wherein the upward coating apparatus is an upwardsputtering apparatus comprising a lower sputtering target positionedbeneath the path of substrate travel, and wherein said operation of theupward coating apparatus comprises establishing a plasma adjacent saidlower sputtering target.
 19. The method of claim 9 wherein the upwardcoating apparatus is an evaporation coating apparatus, and wherein saidoperation of the upward coating apparatus comprises positioning a sourceof coating material to be evaporated in a lower region of the coater.20. The method of claim 9 wherein the upward coating apparatus is achemical vapor deposition apparatus, and wherein said operation of theupward coating apparatus comprises delivering precursor gas to a lowerregion of the coater.
 21. The method of claim 9 wherein the upwardcoating apparatus comprises a further ion gun, said further ion gunbeing adapted for ion beam coating deposition, and wherein saidoperation of the upward coating apparatus comprises operating saidfurther ion gun to emit an ion beam toward the bottom major surface ofthe substrate.
 22. A coater adapted for applying coating onto asheet-like substrate, the coater comprising a substrate support defininga path of substrate travel extending through the coater, a downwardcoating apparatus positioned above the path of substrate travel andadapted for coating a top major surface of the substrate, and an ion gunpositioned beneath the path of substrate travel and adapted for cleaninga bottom major surface of the substrate, wherein the ion gun is at alocation further along the path of substrate travel than the downwardcoating apparatus such that the ion gun is adapted to remove from thebottom major surface of the substrate oversprayed coating inadvertentlydeposited upon marginal portions of the bottom major surface of thesubstrate during operation of the downward coating apparatus.
 23. Thecoater of claim 22 wherein the substrate support is configured formaintaining the substrate in a horizontal orientation during conveyanceof the substrate through the coater.
 24. The coater of claim 22 whereinthe substrate is a sheet of glass positioned on the substrate support,and wherein other sheets of glass are also positioned on the substratesupport, such sheets of glass being spaced-apart from one another on thesubstrate support.
 25. The coater of claim 22 wherein the substratesupport comprises a plurality of spaced-apart transport rollers.
 26. Thecoater of claim 25 wherein the ion gun is adapted to emit an ion beamupwardly between an adjacent pair of the spaced-apart transport rollers.27. The coater of claim 26 wherein said adjacent pair of rollers arespaced further apart than other adjacent rollers in the coater.
 28. Thecoater of claim 22 wherein the downward coating apparatus is a downwardsputtering apparatus comprising an upper sputtering target positionedabove the path of substrate travel.
 29. The coater of claim 22 whereinthe downward coating apparatus is a chemical vapor deposition apparatuscomprising at least one gas-delivery outlet for delivering precursor gasto an upper region of the coater.
 30. The coater of claim 22 wherein thedownward coating apparatus comprises an upper ion gun, the upper ion gunbeing adapted for ion beam coating deposition and positioned above thepath of substrate travel.
 31. The coater of claim 22 further comprisingan upward coating apparatus, the upward coating apparatus beingpositioned beneath the path of substrate travel and adapted for coatingthe bottom major surface of the substrate, wherein the upward coatingapparatus is at a location further along the path of substrate travelthan the ion gun, such that the upward coating apparatus is adapted forcoating the bottom major surface of the substrate after the ion gun hasbeen operated to clean oversprayed coating from the bottom major surfaceof the substrate.
 32. The coater of claim 31 wherein the coater does nothave any downward coating apparatus further along the path of substratetravel than the upward coating apparatus, such that marginal portions ofcoating applied to the bottom major surface of the substrate will not beconcealed by oversprayed coating from any subsequent downward coatingapparatus in the coater.
 33. The coater of claim 31 wherein the upwardcoating apparatus is disposed in a final chamber of the coater.
 34. Thecoater of claim 31 wherein the upward coating apparatus is configuredfor deposition of a surface-effect coating selected from the groupconsisting of a photocatalytic coating, a hydrophilic coating, and ahydrophobic coating, the upward coating apparatus including a source ofcoating material comprising titanium and/or silicon.
 35. The coater ofclaim 31 wherein the upward coating apparatus is an upward sputteringapparatus comprising a lower sputtering target positioned beneath thepath of substrate travel.
 36. The coater of claim 31 wherein the upwardcoating apparatus is an evaporation coating apparatus comprising asource of coating material to be evaporated in a lower region of thecoater.
 37. The coater of claim 31 wherein the upward coating apparatusis a chemical vapor deposition apparatus comprising at least onegas-delivery outlet for delivering precursor gas to a lower region ofthe coater.
 38. The coater of claim 31 wherein the upward coatingapparatus comprises a further ion gun, the further ion gun being adaptedfor ion beam coating deposition.
 39. A method of processing a sheet-likesubstrate, the method comprising: a) providing a coater adapted forapplying coating onto the substrate, the coater comprising a substratesupport defining a path of substrate travel extending through thecoater, wherein an ion gun is positioned beneath the path of substratetravel, and wherein an upward coating apparatus is positioned beneaththe path of substrate travel at a location further along the path ofsubstrate travel than the ion gun; b) conveying the substrate along thepath of substrate travel; c) operating the ion gun to emit an ion beamtoward a bottom major surface of the substrate, the ion beam comprisingaccelerated ions that strike the bottom major surface of the substrate;and d) operating the upward coating apparatus to deposit aphotocatalytic coating on the bottom major surface of the substrate. 40.The method of claim 39 wherein the upward coating apparatus is an upwardsputtering apparatus comprising a lower sputtering target positionedbeneath the path of substrate travel, the lower target being sputteredto deposit the photocatalytic coating on the bottom major surface of thesubstrate.
 41. The method of claim 40 wherein the lower target comprisesa titanium-containing target material, the lower target being sputteredin an oxidizing atmosphere.
 42. The method of claim 39 wherein thephotocatalytic coating is deposited so as to have a total opticalthickness of less than about 690 Å.
 43. The method of claim 39 whereinsaid operation of the upward coating apparatus to apply thephotocatalytic coating is performed after all other coating of thesubstrate in the coater has been performed.
 44. The method of claim 39wherein the substrate is not conveyed beneath any operating downwardcoating apparatus in the coater after said operation of the upwardcoating apparatus, such that marginal portions of coating applied to thebottom major surface of the substrate will not be concealed byoversprayed coating from any subsequent downward coating apparatus inthe coater.
 45. The method of claim 39 wherein said operation of theupward coating apparatus is performed in a final chamber of the coater.46. The method of claim 39 wherein the ion gun is at a location furtheralong the path of substrate travel than a downward coating apparatus,the method comprising operating the downward coating apparatus to coat atop major surface of the substrate, said operation of the ion gun beingperformed to remove from the bottom major surface of the substrateoversprayed coating inadvertently deposited upon marginal portions ofthe bottom major surface of the substrate during said operation of thedownward coating apparatus.
 47. A coater adapted for applying coatingonto a sheet-like substrate, the coater comprising a substrate supportdefining a path of substrate travel extending through the coater,wherein an ion gun is positioned beneath the path of substrate travel,and wherein an upward coating apparatus is positioned beneath the pathof substrate travel at a location further along the path of substratetravel than the ion gun, the upward coating apparatus comprising a lowersputtering target comprising a titanium-containing target material.